An ultrasound diagnostic apparatus can generate an ultrasonic image representing information on the inside of a biological body in a non-invasive manner and display the image thus generated substantially in real time. In diagnoses of cardiac diseases, ultrasound diagnostic apparatuses are used for quantitatively assessing wall motion information of the heart in echocardiography.
Left ventricular end diastolic pressure (LVEDP) is an important index used for diagnoses of cardiac diseases. LVEDP is an index reflecting the left ventricular diastolic function (specifically, compliance of the left ventricle) of a heart and is an important diagnostic index in diagnoses and treatments of cardiac diseases. For example, it is known that a heart with high LVEDP has a poor prognosis. To measure LVEDP accurately, invasive cardiac catheter tests are required, which are not usually used in clinical practices.
In clinical practices, “E/e′” that can be measured by non-invasive method in echocardiography is used as an index for estimating LVEDP. “E/e′” is widely known as an index correlating with left ventricular filling pressure and LVEDP, and can be measured using the pulsed wave (PW) Doppler method. “E” corresponds to the wave height at early diastole in a waveform of left ventricular inflow velocities plotted along the cardiac time phase (wave height of E-waves). Measurement of “E”, for example, is performed by setting a range gate at the mitral orifice and collecting blood flow PW Doppler waveforms. “e′” corresponds to the wave height at early diastole in a waveform of mitral annulus tissue velocities plotted along the cardiac time phase. Measurement of “e′”, for example, is performed by setting a range gate at the mitral annulus and collecting tissue PW Doppler waveforms. “E/e′” is calculated as the ratio between “E” and “e′”.
To calculate “E/e′”, both left ventricular inflow blood velocities and mitral annulus tissue velocities need to be measured. “E” and “e′” have conventionally been measured from different heart beats. There are cases, however, where “E/e′” calculated using “E” and “e′” measured from different heart beats shows low accuracy. For the reason described above, in recent years, measurement of “E” and “e′” has been simultaneously performed from the same heart beat using a technique with which Doppler waveforms in two regions can be simultaneously collected by performing PW Doppler scanning on a time sharing basis. With this technique, however, “E/e′” is not always an index accurately reflecting the LVEDP.